It is necessary in a number of medical diagnostic procedures to place electrodes on the body of a patient. If the measuring points are located in readily accessible areas with the patient in the recumbent position, for example, in the chest area, the electrodes can usually be fastened without any major difficulties. For certain measuring procedures, such as electric impedance tomography (EIT), an electrode carrier with, e.g., 16 or 32 electrodes must be placed around the patient's chest in order to make it possible to measure the surface potentials along a section plane through the patient's body. Such a tomogram of the impedance distribution is used to visualize and monitor the ventilation of the lung as well as the blood or serum shift in a regionally resolved manner.
The placement of the electrode carrier does not usually cause any problems in case of mobile patients who can raise their upper bodies themselves. By contrast, it is difficult to fasten an electrode carrier extending around the chest in case of respirated patients lying unconscious in bed. This is usually possible only by turning the patient several times. Such a manipulation is highly burdensome in case of severely ill patients for both the health care personnel and the patient.
It is known that variable-pressure cushions are placed on the bed for bedridden patients in order to prevent decubital necroses on the back. In prior-art variable-pressure cushions, pressure is alternatingly admitted into two groups of cells located close next to each other. A reversing valve connects a pressurized gas source with one of the cell groups each, while the other cell group is depressurized. A massaging effect and stimulation of the blood circulation are achieved as a result. A novel variable-pressure cushion is known from EP 448 555 B1. The prior-art variable-pressure cushion is designed for dynamic applications with short pressure change cycles.